Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager
Summary
Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name. It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.
What this means
In plain English
Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name. It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.
Recommended action
Primary action: update to a vendor-listed fixed release: 3.8.6, 3.9.5. Temporary workaround: Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.
Rewritten locally from the scraped official advisory data above; no generative API is used. The vendor advisory is authoritative.
- Apache ZooKeeper 3.9.0 through 3.9.4
- Apache ZooKeeper 3.8.0 through 3.8.5
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
- 3.8.6
- 3.9.5
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
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